have you cleaned the battery terminals and cable ends, wire brush or scrape with sharp edge. ive seen batteries that would not hold a charge. have not seen it happen from one start to the next. it was more of a left the key on in the forklift and run the battery down one two many times. forklift would run as long as we jumpstarted it otherwise it would do nothing. i have seen dirty battery terminals do the same thing with a good battery.

 

^ Thats very true too. Terminals could be getting a bad connection.